You've heard of Christopher Columbus. You've read about the Vikings. But who made the first-ever sea voyage? According to one archaeologist's radical new theory, the first sailors weren't quite human.

Robert G. Bednarik thinks that the first species to build a boat and make an ocean journey was not our own, Homo sapiens , but our predecessor, Homo erectus . The latter is the humanlike species that existed before H. sapiens and may have been our direct ancestor. H. erectus had slightly smaller brains set in longer, lower braincases than ours.

If Bednarik is right, the first ocean voyage took place not 40,000 years ago, but as early as 800,000 years ago¡ªwhen H. erectus may have traveled from the island of Bali to neighboring islands in southern Indonesia .

To test his theory, Bednarik had a bamboo raft built using stone tools like those H. erectus might have had. He and 11 crewmembers then paddled the raft 18 miles across rough waters from Bali to the island of Lombok . On their first trial voyage, the ocean currents pushed the crew too far north, and they had to give up. On their second trial, one of the crewmembers collapsed from exhaustion. But they finally made it¡ªand if they could do it, Bednarik says, so could H. erectus , 800,000 years ago.

Not everyone agrees. Some researchers say that H. erectus didn't have the intelligence to build a boat or to plan a journey. Instead, members of that species might have drifted to Lombok and other islands on huge, floating masses of seaweed that are strong enough to support a person.